Radiological Case: Intra-abdominal pregnancy

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CASE SUMMARY

A 24-year-old, primigravida woman was referred at 28 weeks
gestational age for Doppler studies to rule out intrauterine growth
retardation. She had undergone regular obstetric follow up elsewhere,
including a dating scan which confirmed a single live intrauterine
gestation with adequate interval growth. At 2 months amenorrhea she gave
a history of acute abdominal pain associated with spotting per vaginum.
Emergency ultrasound done elsewhere at that time confirmed the presence
of single live intrauterine gestation. She was given hormonal support
and advised to remain on bed rest. Her pregnancy continued uneventfully
until she went to a nearby government hospital for a routine checkup,
when she was clinically diagnosed as IUGR and referred to our institute
for fetal Doppler evaluation.

IMAGING FINDINGS

Real-time sonography demonstrated a single live fetus in transverse
lie with the fetal head in left lumbar region.The bulky empty uterus was
seen separately in the pelvis posterior to the bladder (Figures 1,2).
There was no demonstrable uterine myometrium around the fetus (Figure
3). Fetal biometric data was consistent with 23-24 weeks gestation as
opposed to the expected gestational age of 27-28 weeks. Amniotic fluid
was scanty (Figure 4). The placenta was localized to the right
hypochondrium (Figure 5), with minimal free fluid in the Pouch of
Douglas. As a separate uterus was identified away from the fetus, the
possibilities of pregnancy in a uterine diadelphys or pregnancy in a
uterine horn were considered. But the absence of myometrial tissue
around the fetus and presence of free fluid in POD outlining the fetal
head without intervening myometrium (Figure 3) ruled out these
possibilities. Consequently, a diagnosis of intra-abdominal pregnancy
was made. Doppler US of the umbilical artery revealed a high resistive
index of 8 (Figure 6).

An MRI examination was subsequently performed with a 1.5T Siemens
Emotion Duo in all three orthogonal planes with HASTE sequence. A fetus
surrounded by a thin amniotic membrane was demonstrated to lie in the
transverse position within the abdominal cavity (Figure 7). No
myometrium was visualized around the fetus. The placenta was seen in the
right hypochondrium with displacement of adjacent maternal bowel loops
and implantation into fat intensity structure possibly omentum (Figure
8). Very few amniotic pockets were seen surrounding the fetus. The
maternal urinary bladder, rectum and bowel loops were found to be
relatively free of the fetal sac. The uterus was found separately in the
pelvis with its posterosuperior wall adhering to the fetal sac.

In view of severe fetal IUGR and high risks associated with
continuing the pregnancy, the patient was advised to terminate her
pregnancy. Accordingly, a laparotomy was performed. Preoperative
findings matched our antenatal imaging findings (Figure 9). A live IUGR
male baby weighing approximately 500 g with Apgar 4/10, 6/10 was
delivered and shifted to the NICU for ventilator support. The placenta,
still attached to the omentum, was released with difficulty. There were
dense adhesions between the posterosuperior aspect of the uterus and the
amniotic membrane. The right tube and ovary were found to be normal
while the left tube and ovary could not be visualized because of dense
adhesions. The placenta was removed in toto and the abdomen closed in
layers. Four units of blood were transfused intraoperatively. The
postoperative period was uneventful.

DIAGNOSIS

Intra-abdominal pregnancy

DISCUSSION

Intra-abdominal pregnancy is a type of ectopic pregnancy wherein the
fetus grows in the abdominal cavity. The extrauterine implantation can
occur in the omentum, the large vessels or even in the vital organs.
Abdominal pregnancies account for 0.1% of all pregnancies and up to 1.4%
of ectopic pregnancies.1 These pregnancies can go undetected until an advanced gestational age and often result in massive hemorrhage.2 Rates of maternal mortality range between 2 and 30%3.
Advanced abdominal pregnancy carries a risk of hemorrhage, disseminated
intravascular coagulation, bowel obstruction and fistulae to the
gastrointestinal and/or genitourinary tracts.3 The site of
implantation and availability of vascular supply determine the
possibility of fetal survival. Risk factors associated with abdominal
pregnancy include tubal damage, pelvic inflammatory disease,
endometriosis, assisted reproductive techniques and multiparity.
Clinical history and physical examination alone may be insufficient to
make a preoperative diagnosis. Sonography is the most effective method
for diagnosing an abdominal pregnancy. MRI is an emerging important,
complementary imaging modality that helps not only to confirm the
diagnosis but also to delineate the precise anatomical relationship
between the fetus and various maternal abdominal organs.

Abdominal pregnancy occurs either as a result of tubal abortion or
rupture (secondary abdominal pregnancy) or rarely as a result of primary
peritoneal implantation (primary abdominal pregnancy). 1Primary
peritoneal implantation is rare. Studdiford established three criteria
for diagnosing primary peritoneal pregnancies: (1) normal bilateral
fallopian tubes and ovaries; (2) the absence of uteroperitoneal fistula;
and (3) a pregnancy related exclusively to the peritoneal surface and
early enough to eliminate the possibility of secondary implantation
following a primary nidation in the tube.4

The mortality of abdominal pregnancy is 7.7 times higher than that of
tubal pregnancy and 90 times greater than that of intrauterine
pregnancy.5 Associated morbidities include hemorrhage,
disseminated intravascular coagulation, bowel obstruction and fistulae
formation due to fetal bones protruding through thin amniotic membranes.
Fetal malformations such as torticollis, facial asymmetry, malformation
of limbs, flattening of the head and thorax, etc., may occur due to
severe oligohydramnios.2

Abdominal pain is the most frequent symptom. Rarely, symptoms may
relate to placental site attachment, including attachment to the bowel
or bladder obstruction.

Sonographic features denoting abdominal pregnancy include fetus being
seen outside the uterine cavity, absence of the uterine wall between
bladder and fetal parts, oligohydramnios, fetal parts located close to
the maternal abdominal wall, and abnormal location of placenta outside
the uterine cavity.5 Sonography remains the imaging modality
of choice for the evaluation of abdominal pregnancy when abnormal
relationships among the fetus, uterus, placenta and amniotic fluid are
made.6 It is also useful in assessing fetal congenital malformations usually associated with abdominal pregnancies.

The role of MRI is to locate the placenta and identify its adherence
to any vital organs, including the liver and spleen. In this case, MRI
not only helped confirm the diagnosis, but it delineated the exact
anatomical localization of fetal parts and placental tissue as well as
the adhesions to the uterus. This information proved vital in
preoperative planning. The information on the location, state of
viability of the placenta and blood supply will influence management and
aid in planning surgery.7 MRI has many advantages over ultrasound as bone, gas-filled structures and maternal obesity provides no hindrance to imaging.

Preoperative angiograms can be useful in locating all sources of
vascular supply to the placenta and if possible to embolize vessels
difficult to ligate operatively. If the placenta is not removed during
laparotomy, postoperative embolization of feeding arteries can be done
to control hemorrhage from adherent placenta.5

Previous scans of our patient were read as an intrauterine pregnancy.
She also had a history of first-trimester abdominal with spotting per
vaginum, which might have been due to either a tubal abortion or a tubal
rupture with the conceptus getting implanted into the peritoneal
cavity.This had gone unnoticed with the fetus growing as an abdominal
pregnancy. Approximately 50% of ectopic pregnancies are missed at the
time of initial presentation. Advanced abdominal pregnancy is rare and
accounts for 1 in 25,000 pregnancies.8

The management of abdominal pregnancy depends on fetal viability,
presence of fetal congenital abnormalities, fetal gestational age,
maternal complications, placental location and adherence. Usually
surgical intervention is necessary regardless of fetal viability. The
management of the placenta is still under debate. Total removal is
preferable with ligation of blood supply or preoperative embolization.
Partial removal due to adherence may result in massive hemorrhage and
shock.3 In cases of adherence the placenta can be left in
situ, ligating the cord as close to the placenta as possible. The
placenta usually ceases to function after 4 months.2 Postoperative
angiographic embolization of feeder vessels is possible and placental
involution can be followed by serial bHCG. Some authors advocate
preoperative systemic methotrexate in the management of abdominal
pregnancy.9